Vietnam visa stamp delay

Is there any delay to get the visa stamp in my passport at the Hanoi airport or it is the same way to go like the tourist that has already the visa stamp in the passport?

Vietnam visa on arrival for second entry by land

I am visiting Vietnam in December 2015. My itinerary is as following: arriving in Vietnam on December 3, 2015 by air, and then leaving the country for Laos on December 21, 2015 and then coming back to Vietnam on December 25, 2015 and finally leaving Vietnam for my home on December 29, 2015. Can I use Vietnam visa on arrival?